The EDR is an alternate way to express the energy performance of a home using a scoring system where 100 represents the energy performance of a reference design building meeting the envelope requirements of the 2006 IECC. The EDR is similar to the energy rating index in the 2015 IECC and the 2014 RESNET standard. Combining high levels of energy efficiency with generating renewable energy, a score of zero or less can be achieved.
Buildings complying with the current Energy Code are more efficient than the 2006 IECC, so most newly constructed buildings will have EDR scores below 100. Buildings with renewable generation like PV can achieve a negative score. If EDRs were calculated for an older inefficient home, the score would likely be well over 100.
There are two EDRs used to evaluate single-family residential buildings. EDR1 is based on source energy and the proposed design EDR1 must be equal to or less than the standard design EDR1. EDR2 is based on TDV energy and has two components that must be met for compliance. The EDR2 score of proposed efficiency must be equal to or less than the EDR2 score of the standard efficiency, and the total proposed EDR2 score must be equal to or less than the total standard design EDR2.